1. Field of the Invention
This invention relates broadly to a pulse processor, and more particularly to an autocorrelated pulse processor suitable for use with electro-optical gaging systems and the like.
2. Description of the Prior Art
Electro-optical gaging systems are used in a variety of industrial applications. Many such gaging systems operate on the principle of back lighting an object to be measured and imaging a shadow of the object through a lens onto the face of an electronic camera. A photoresponsive image detector in the camera generates a raw camera pulse having a width that approximates the dimension between shadow edges. Raw camera pulses are processed in edge detection circuitry which attempts to more closely define camera pulse width in relation to the object dimension.
Early attempts at dimensional gaging comprised chopped light sources, a photocell detector and an image pulse processor involving pulse differentiation in an edge detection circuit. This gaging arrangement was slow in responding to object dimensional changes, possessed a great deal of differentiator noise and exhibited unsatisfactory gage accuracy for many applications. Later developments aimed at improving the differentiator noise problem involved the addition of a comparator and gate to the differentiator in edge detection circuitry met with some limited success.
However, none of the prior art pulse processors is entirely suitable for use in dimensional gages to be installed in contemporary high-speed steel bar rolling mills. In order to meet bar dimensional control requirements, measurements must be made at high repetitive speeds of about 300 Hz in the rolling mill environment. Considerable switching noise occurs at such measuring speeds, and differentiator noise is particularly troublesome. Electrical noises in the severe environment of the rolling mill further compound the problem of making definitive bar measurements at high accuracy, high resolution and high reliability. None of the prior art pulse processing arrangements met these requirements.